#include <stdio.h>
int main()
{
	int soda = 0;
	int bottle = 0;
	float money = 20;
	
	while(money > 1)
	{
		bottle = 0;
		while(money > 0.5)
		{
			money--;
			bottle++;
			soda++;
		}
		
		money = bottle * 0.5;
	}
	
	printf("%d ", soda);
	return 0;
}


